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Conversion Information and Constants:
| 1 atmosphere |
= 1.013 bar |
| 1 atmosphere |
= 14.5 pound per square inch (psi) |
| 1 Revolution |
= 2pi radians |
| 1 RPM |
= 376.98 rad/sec |
| 1 inch |
= 25.4 mm |
| 1 metre |
= 3.28 ft |
| 1 kg |
= 2.205 lbs |
| 1kJ |
= 1000Nm |
| 1000Nm |
= 0.948 BTu |
| 1000Nm |
= 737.6 ft lbf |
| 1kW |
= 1kJ/s |
| 1 hp |
= 746 W |
| g, acceleration due to gravity |
= 9.80 metres/second/second |
| 1mph |
= 1.609 kph |
| 1g |
= 0.305 oz |
| 1kgm^3 |
= 0.062 lb/ft^3 |
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Engineering Equations:
Electrical Equations
| I = V/R |
I - Current, V - Volts, R - Resistance |
| P =V*I |
P - Power, V - Volts, I - Current |
| Heating is proportional
to I^2 |
I - Current |
| E = VIt |
E - Electrical energy (joules), V - Volts, I - Current, t - Time
(seconds) |
| Battery current * battery voltage = Motor
current * Motor speed |
Assumes speed controller is 97-99% efficient (eg. 4QD). |
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Mechanical Equations
| RPM = (S * Gear-ratio * 168)/WR |
S - Speed in Miles per hour and WR - Wheel Radius in Inches |
| To calculate acceleration / deceleration energy,
E=1/2mv2 |
E -Kinetic Energy (joules), m - Mass (kg),
v - Velocity (metres/second) |
To calculate energy required to climb a hill,
E=mgh
Or, for gradient T%, E=mg*T/100*Length
of hill |
E - Potential Energy (joules), m - Mass (kg), g - gravity (9.80
m/s/s), h - height to climb (m) |
| Motor speed is
inversely
proportional to Motor
power |
| HP = (S * T) / 7118 |
HP - Horse Power, S - Speed (RPM), T - Torque
(Nm) |
| P = S * T |
P - Power, S - Speed (rad/sec), T - Torque (Nm) |
| Density = mass / volume |
Mass (g), Volume (cm cubed) |
To calculate the amount of material removed by drilling holes in it, use the calculator below.
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Physical Properties:
Bernoulli's Equation
| P + 0.5p * v^2 + pgh = Constant |
P - fluid pressure, p - fluid density
v - fluid velocity, g - 9.80 m/s/s
h - height of fluid above reference line |
Boyle's Law
| (P1*V1)/T1 = (P2*V2)/T2 |
P1, P2 - fluid pressure; V1, V2 - volume of fluid; T1, T2 - temperature.
For normal robots, assume T1=T2. |
Conductivity Of Metals
|
Conductivity |
Specific Heat |
| Thermal |
Electrical |
| Aluminium |
50 |
339 |
20 |
| Copper |
92 |
562 |
9 |
| Gold |
70 |
413 |
3 |
| Lead |
8 |
48 |
3 |
| Silver |
100 |
602 |
6 |
| Steel |
11 |
50 |
10 |
Specific heat = thermal
mass / actual mass
Thermal Conductivity
is related to volume |
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Gearing Systems
 Gear ratios
are calculated on a product basis. In the example here, we have a drive
system using 4 gears of 30 (grey and red), 50 (blue) and 80 (black) teeth.
The gear ratio for the grey-blue pair is therefore 5:3, for the red-black
pair, 8:3 giving a total ratio of 5:3 * 8:3, giving 40:9. Remember also
that gears are sold in mod groups. A mod is a way of specifying the size
and shape of the gear teeth. For gears to mesh, they must be of the same
mod set (eg. both mod 2). |
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